Memory Arrays Comprising Strings Of Memory Cells And Methods Used In Forming A Memory Array Comprising Strings Of Memory Cells

ABSTRACT

A memory array comprising strings of memory cells comprises a conductor tier comprising conductor material. The memory array comprises laterally-spaced memory blocks individually comprising a vertical stack comprising alternating insulative tiers and conductive tiers directly above the conductor tier. Conducting material of a lowest of the conductive tiers is directly against the conductor material of the conductor tier. Channel-material strings of memory cells extend through the insulative tiers and the conductive tiers. Intervening material is laterally-between and longitudinally-along immediately-laterally-adjacent of the memory blocks. The conducting material in the lowest conductive tier is directly against the channel material of individual of the channel-material strings. Conductive material is of different composition from that of the conducting material above and directly against the conducting material. Other embodiments, including method, are disclosed.

TECHNICAL FIELD

Embodiments disclosed herein pertain to memory arrays and to methodsused in forming a memory array.

BACKGROUND

Memory is one type of integrated circuitry and is used in computersystems for storing data. Memory may be fabricated in one or more arraysof individual memory cells. Memory cells may be written to, or readfrom, using digitlines (which may also be referred to as bitlines, datalines, or sense lines) and access lines (which may also be referred toas wordlines). The sense lines may conductively interconnect memorycells along columns of the array, and the access lines may conductivelyinterconnect memory cells along rows of the array. Each memory cell maybe uniquely addressed through the combination of a sense line and anaccess line.

Memory cells may be volatile, semi-volatile, or non-volatile.Non-volatile memory cells can store data for extended periods of time inthe absence of power, Non-volatile memory is conventionally specified tobe memory having a retention time of at least about 10 years. Volatilememory dissipates and is therefore refreshed/rewritten to maintain datastorage. Volatile memory may have a retention time of milliseconds orless. Regardless, memory cells are configured to retain or store memoryin at least two different selectable states. In a binary system, thestates are considered as either a “0” or a “1”. In other systems, atleast some individual memory cells may be configured to store more thantwo levels or states of information.

A field effect transistor is one type of electronic component that maybe used in a memory cell. These transistors comprise a pair ofconductive source/drain regions having a semiconductive channel regionthere-between. A conductive gate is adjacent the channel region andseparated there-from by a thin gate insulator. Application of a suitablevoltage to the gate allows current to flow from one of the source/drainregions to the other through the channel region. When the voltage isremoved from the gate, current is largely prevented from flowing throughthe channel region. Field effect transistors may also include additionalstructure, for example a reversibly programmable charge-storage regionas part of the gate construction between the gate insulator and theconductive gate.

Flash memory is one type of memory and has numerous uses in moderncomputers and devices. For instance, modern personal computers may haveBIOS stored on a flash memory chip. As another example, it is becomingincreasingly common for computers and other devices to utilize flashmemory in solid state drives to replace conventional hard drives. As yetanother example, flash memory is popular in wireless electronic devicesbecause it enables manufacturers to support new communication protocolsas they become standardized, and to provide the ability to remotelyupgrade the devices for enhanced features.

NAND may be a basic architecture of integrated flash memory. A NAND cellunit comprises at least one selecting device coupled in series to aserial combination of memory cells (with the serial combination commonlybeing referred to as a NAND string). NAND architecture may be configuredin a three-dimensional arrangement comprising vertically-stacked memorycells individually comprising a reversibly programmable verticaltransistor. Control or other circuitry may be formed below thevertically-stacked memory cells. Other volatile or non-volatile memoryarray architectures may also comprise vertically-stacked memory cellsthat individually comprise a transistor.

Memory arrays may be arranged in memory pages, memory blocks and partialblocks (e.g., sub-blocks), and memory planes, for example as shown anddescribed in any of U.S. Patent Application Publication Nos.2015/0228651, 2016/0267984, and 2017/0140833. The memory blocks may atleast in part define longitudinal outlines of individual wordlines inindividual wordline tiers of vertically-stacked memory cells.Connections to these wordlines may occur in a. so-called “stair-stepstructure” at an end or edge of an array of the vertically-stackedmemory cells. The stair-step structure includes individual “stairs”(alternately termed “steps” or “stair-steps”) that define contactregions of the individual wordlines upon which elevationally-extendingconductive vias contact to provide electrical access to the wordlines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional view of a portion of asubstrate in process in accordance with an embodiment of the inventionand is taken through line 1-1 in FIG. 2.

FIG. 2 is a diagrammatic cross-sectional view taken through line 2-2 inFIG. 1.

FIGS. 3-4 are enlarged views of portions of FIGS. 1 and 2.

FIGS. 5-26 are diagrammatic sequential sectional, expanded, enlarged,and/or partial views of the construction of FIGS. 1-4, or portionsthereof, in process in accordance with some embodiments of theinvention.

FIG. 27 is a diagrammatic cross-sectional view of another portion of theFIGS. 2 and 21 substrates.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Embodiments of the invention encompass methods used in forming a memoryarray, for example an array of NAND or other memory cells that may haveat least some peripheral control circuitry under the array (e.g.,CMOS-under-array). Embodiments of the invention also encompass a memoryarray (e.g., NAND architecture) independent of method of manufacture.First example method embodiments are described with reference to FIGS.1-26 which may be considered as a “gate-last” or “replacement-gate”process, and starting with FIGS. 1-4.

FIGS. 1 and 2 show a construction 10 having an array or array area 12 inwhich elevationally-extending strings of transistors and/or memory cellswill be formed. Construction 10 comprises a base substrate 11 having anyone or more of conductive/conductor/conducting,semiconductive/semiconductor/semiconducting, orinsulative/insulator/insulating (i.e., electrically herein) materials.Various materials have been formed elevationally over base substrate 11.Materials may be aside, elevationally inward, or elevationally outwardof the FIGS. 1-4-depicted materials. For example, other partially orwholly fabricated components of integrated circuitry may be providedsomewhere above, about, or within base substrate 11, Control and/orother peripheral circuitry for operating components within an array(e.g., array 12) of elevationally-extending strings of memory cells mayalso be fabricated and may or may not be wholly or partially within anarray or sub-array. Further, multiple sub-arrays may also be fabricatedand operated independently, in tandem, or otherwise relative oneanother. In this document, a “sub-array” may also be considered as anarray.

A conductor tier 16 comprising conductor material 17 (e.g.,conductively-doped polysilicon atop WSi_(x)) has been formed abovesubstrate 11. Conductor tier 16 may comprise part of control circuitry(e.g., peripheral-under-array circuitry and/or a common source line orplate) used to control read and write access to the transistors and/ormemory cells that will be formed within array 12. A stack 18 comprisingvertically-alternating insulative tiers 20* and conductive tiers 22* hasbeen formed above conductor tier 16 (an * being used as a suffix to beinclusive of all such same-numerically-designated components that may ormay not have other suffixes). Example thickness for each of tiers 20*and 22* is 22 to 60 nanometers. Only a small number of tiers 20* and 22*is shown, with more likely stack 18 comprising dozens, a hundred ormore, etc. of tiers 20* and 22*. Other circuitry that may or may not bepart of peripheral and/or control circuitry may be between conductortier 16 and stack 18. For example, multiple vertically-alternating tiersof conductive material and insulative material of such circuitry may bebelow a lowest of the conductive tiers 22* and/or above an uppermost ofthe conductive tiers 22*. For example, one or more select gate tiers(not shown) may be between conductor tier 16 and the lowest conductivetier 22* and one or more select gate tiers may be above an uppermost ofconductive tiers 22*. Alternately or additionally, at least one of thedepicted uppermost and lowest conductive tiers 22* may be a select gatetier. Regardless, conductive tiers 22* (alternately referred to as firsttiers) may not comprise conducting material and insulative tiers 20*(alternately referred to as second tiers) may not comprise insulativematerial or be insulative at this point in processing in conjunctionwith the hereby initially-described example method embodiment which is“gate-last” or “replacement-gate”. Example conductive tiers 22* comprisefirst material 26 (e.g., silicon nitride) which may be wholly orpartially sacrificial. Example insulative tiers 20* comprise secondmaterial 24 (e.g., silicon dioxide) that is of different compositionfrom that of first material 26 and which may be wholly or partiallysacrificial.

In some embodiments, a lowest first tier 22 z is thicker than the firsttiers 22* there-above and in one such embodiment is at least 1.5 timesthicker than first tiers 22* there-above. In one embodiment and asshown, lowest first tier 22 z is not directly against conductor material17 of conductor tier 16, for example where a lowest second tier 20 z isvertically between conductor material 17 of the conductor tier 16 andlowest first tier 22 z. Alternately, the lowest first tier may bedirectly against the conductor material of the conductor tier (notshown). In one embodiment, lowest second tier 20 z is directly against atop 19 of conductor material 17 of conductor tier 16. In one embodiment,lowest second tier 20 z is thinner than second tiers 20* there-above. Inone embodiment, the second tier 20 x that is immediately-above lowestfirst tier 22 z (i.e., next-higher second tier 20 x) is thicker thansecond tiers 20* there-above.

The second-tier material of second tier 20 x that is immediately-abovelowest first tier 22 z (i.e., there being no other second tiervertically between lowest first tier 22 z and said second tier 20 ximmediately-there-above) comprises an upper first insulative material 21and a lower second material 23 under upper first insulative material 21,with lower second material 23 being of different composition from thatof upper first insulative material 21. In one such embodiment, lowersecond material 23 is thinner than upper first insulative material 21.Regardless, upper insulative material 21 may be of the same compositionas material 24. In some embodiments, the second-tier material of secondtier 20 x that is immediately-above lowest first tier 22 z may beconsidered as comprising an upper insulative material 21, a lowermaterial 27, and an intermediate material 23 vertically-between upperinsulative material 21 and lower material 27, with intermediate material23 being of different composition from that of lower material 27 andfrom that of upper insulative material 21 (lower material 27 beingoptional in some embodiments). In some such embodiments, upperinsulative material 21 and lower material 27 are of the same thicknessas one another. Regardless, in some embodiments upper insulativematerial 21 and lower material 27 are of the same composition relativeone another (e.g., and the same composition as material 24) and in otherembodiments are of different composition relative one another. In someembodiments, lower second material 23/intermediate material 23 comprisesat least one of conductively-doped polysilicon, polysilicon that is notconductively doped, carbon-doped polysilicon, silicon nitride, undopedsilicon nitride, carbon-doped silicon nitride, and metal material.

Channel openings 25 have been formed (e.g., by etching) throughinsulative tiers 20* and conductive tiers 22* to conductor tier 16.Channel openings 25 may taper radially-inward (not shown) moving deeperin stack 18. In some embodiments, channel openings 25 may go intoconductor material 17 of conductor tier 16 as shown or may stopthere-atop (not shown). Alternately, as an example, channel openings 25may stop atop or within the lowest insulative tier 20. A reason forextending channel openings 25 at least to into conductor material 17 ofconductor tier 16 is to provide and anchoring effect to material that iswithin channel openings 25. Etch-stop material (not shown) may be withinor atop conductor material 17 of conductor tier 16 to facilitatestopping of the etching of channel openings 25 relative to conductortier 16 when such is desired. Such etch-stop material may be sacrificialor non-sacrificial.

Horizontally-elongated trenches 40 have been formed (e.g., byanisotropic etching) into stack 18 to form laterally-spaced memory-blockregions 58. Trenches 40 may have respective bottoms that are directlyagainst conductor material 17 (atop or within) of conductor tier 16 (asshown) or may have respective bottoms that are elevationally-coincidentwith or below the bottom or conductor material 17 of conductor tier 16(not shown). By way of example and for brevity only, channel openings 25are shown as being arranged in groups or columns of staggered rows offour and five channel openings 25 per row and being arrayed inlaterally-spaced memory-block regions 58 that will compriselaterally-spaced memory blocks 58 in a finished circuitry construction.In this document, “block” is generic to include “sub-block”.Memory-block regions 58 and resultant memory blocks 58 (not yet shown)may be considered as being longitudinally elongated and oriented, forexample along a direction 55. Any alternate existing or future-developedarrangement and construction may be used.

Transistor channel material may be formed in the individual channelopenings elevationally along the insulative tiers and the conductivetiers, thus comprising individual channel-material strings, which isdirectly electrically coupled with conductive material in the conductortier. Individual memory cells of the example memory array being formedmay comprise a gate region (e.g., a control-gate region) and a memorystructure laterally between the gate region and the channel material. Inone such embodiment, the memory structure is formed to comprise acharge-blocking region, storage material (e.g., charge-storagematerial), and an insulative charge-passage material. The storagematerial (e.g., floating gate material such as doped or undoped siliconor charge-trapping material such as silicon nitride, metal dots, etc.)of the individual memory cells is elevationally along individual of thecharge-blocking regions. The insulative charge-passage material (e.g., aband gap-engineered structure having nitrogen-containing material [e.g.,silicon nitride] sandwiched between two insulator oxides [e.g., silicondioxide]) is laterally between the channel material and the storagematerial.

FIGS. 1-4 show one embodiment wherein charge-blocking material 30,storage material 32, and charge-passage material 34 have been formed inindividual channel openings 25 elevationally along insulative tiers 20*and conductive tiers 22*. Transistor materials 30, 32, and 34 (e.g.,memory-cell materials) may be formed by, for example, deposition ofrespective thin layers thereof over stack 18 and within individualopenings 25 followed by planarizing such back at least to a top surfaceof stack 18.

Channel material 36 has also been formed in channel openings 25elevationally along insulative tiers 20* and conductive tiers 22*, thuscomprising individual operative channel-material strings 53 in channelopenings 25. Channel material 36 may be considered as having a lowestsurface 71 thereof. Channel-material strings 53 in one embodiment havememory-cell materials (e.g., 30, 32, and 34) there-along and withsecond-tier material (e.g., 24) being horizontally-betweenimmediately-adjacent channel-material strings 53. Materials 30, 32, 34,and 36 are collectively shown as and only designated as material 37 inFIGS. 1 and 2 due to scale. Example channel materials 36 includeappropriately-doped crystalline semiconductor material, such as one ormore silicon, germanium, and so-called 111/V semiconductor materials(e.g., GaAs, InP, GaP, and GaN). Example thickness for each of materials30, 32, 34, and 36 is 25 to 100 Angstroms. Punch etching may beconducted to remove materials 30, 32, and 34 from the bases of channelopenings 25 (not shown) to expose conductor tier 16 such that channelmaterial 36 is directly against conductor material 17 of conductor tier16. Such punch etching may occur separately with respect to each ofmaterials 30, 32, and 34 (as shown) or may occur with respect to onlysome (not shown). Alternately, and by way of example only, no punchetching may be conducted and channel material 36 may be directlyelectrically coupled to conductor material 17 of conductor tier 16 onlyby a separate conductive interconnect (not yet shown). Channel openings25 are shown as comprising a radially-central solid dielectric material38 (e.g., spin-on-dielectric, silicon dioxide, and/or silicon nitride).Alternately, and by way of example only, the radially-central portionwithin channel openings 25 may include void space(s) (not shown) and/orbe devoid of solid material (not shown).

Referring to FIGS. 5 and 6, first-tier material 26 (not shown) has beenisotropically etched selectively relative to second-tier material 24(and in one embodiment as shown selectively relative to materials 17,21, 23, and 27) to form void-space 35 in first tiers 22* (e.g., usingliquid or vapor H₃PO₄ as a primary etchant where material 26 is siliconnitride and exposed other materials comprise one or more oxides orpolysilicon). Some of lower second material 23/intermediate material 23may be laterally etched thereby (not shown).

Referring to FIGS. 7 and 8, conducting material 48 has been depositedinto trenches 40 and into void-space 35 in first tiers 22*. Conductingmaterial 48 fills void-space 35 in first tiers 22* that are above lowestfirst tier 22 z and less-than-fills void-space 35 in lowest first tier22 z.

Referring to FIGS. 9-11, conducting material 48 has been etched (e.g.,isotropically) from lowest first tier 22 z. Such may be conductedselectively relative to at least an uppermost portion of conductormaterial 17 of conductor tier 16 and relative to materials 21, 23, and27 as shown. Further, such etching may remove all remaining conductingmaterial 48 that was in trenches 40 from previous processing (as shown).Further, some lateral recessing of material 48 and/or 23 may occur (notshown) relative to sidewalls of trenches 40 as defined by material 24.In one embodiment where lower material 27 is present, and as shown, theetching of conducting material 48 from lowest first tier 22 z isconducted selectively relative to lower material 27 in next-highersecond tier 20 x to leave lower material 27 under intermediate material23 in next-higher second tier 20 x that is immediately-above lowestfirst tier 22 z. The artisan is capable of selecting a suitableisotropic etching chemistry that will etch conducting material 48selectively relative to material 24. As an example, a W conductingmaterial 48 can be isotropically etched selectively relative to a SiO₂material 24 and a polysilicon material 23 using a mixture of ammonia andhydrogen peroxide or a mixture of sulfuric acid and hydrogen peroxide.

FIGS. 12-15 show subsequent processing wherein, in one embodiment,material 30 (e.g., silicon dioxide), material 32 (e.g., siliconnitride), and material 34 (e.g., silicon dioxide or a combination ofsilicon dioxide and silicon nitride) have been etched to expose asidewall 41 of channel material 36 of channel-material strings 53.Regardless, and in one embodiment where lower material 27 is present andas shown in FIG. 11, lower material 27 (not shown in FIGS. 12-14) insecond tier 20 x that is immediately-above lowest first tier 22 z hasbeen etched selectively relative to and to expose a lower surface 31 ofintermediate material 23. As an example, consider an embodiment wherematerial 23 is polysilicon, materials 21, 24, and 27 are silicondioxide, and memory-cell materials 30, 32, and 34 individually are oneor more of silicon dioxide and silicon nitride layers. In such example,the depicted construction can result by using modified or differentchemistries for sequentially etching silicon dioxide and silicon nitrideselectively relative to the other. As examples, a solution of 100:1 (byvolume) water to HF will etch silicon dioxide selectively relative tosilicon nitride, whereas a solution of 1000:1 (by volume) water to HFwill etch silicon nitride selectively relative to silicon dioxide.Accordingly, and in such example, such etching chemistries can be usedin an alternating manner where it is desired to achieve the exampleconstruction shown by FIGS. 14 and 15. The artisan is capable ofselecting other chemistries for etching other different materials wherea construction as shown in FIGS. 14 and 15 is desired. Lower material 27(not shown) is shown as having been removed in the processing of FIG. 12although such may not be removed until later in some embodiments.

Referring to FIGS. 16 and 17, and in one embodiment,conductive/conducting material 42 has been deposited into void-space 35of lowest first tier 22 z under (and in one embodiment directly against)lower second material 23/intermediate material 23 in next-higher secondtier 20 x and directly against exposed sidewall 41 of channel material36 of channel-material strings 53 and directly against an uppermostsurface 43 of conductor material 17 of conductor tier 16. Uppermostsurface 43 may be the same as top 19, for example if none of conductormaterial 17 has been subsequently etched. Such is but one examplewhereby conductive material 42 has been deposited to directlyelectrically couple together channel material 36 of individualchannel-material strings 53 and conductor material 17 of conductor tier16 (e.g., through channel-material sidewall 41). In one embodiment, atleast an uppermost portion of conductor material 17 of conductor tier 16is of the same composition as that of conductive material 42 (e.g., bothbeing conductively-doped polysilicon). Alternately, conductive material42 is of different composition from that of at least an uppermostportion of conductor material 17 of conductor tier 16.

Referring to FIGS. 18 and 19, conductive material 42 has been removedfrom trenches 40, for example by timed isotropic etching that may beconducted selectively relative to materials 21, 23, 24, 48, and 17, Suchmay result in lateral recessing of conductive material 42 in direction39 towards channel-material strings 53 as shown. Such may result in someetching of conductor material 17 when exposed (not shown). An exampleetching chemistry where material 42 is conductively-doped polysilicon,materials 21 and 24 are silicon dioxide, material 23 is silicon nitride,and material 48 is W is tetramethyl ammonium hydroxide. If material 23is of the same composition as conductive material 24, material 23 mayalso be laterally etched thereby (not shown).

Referring to FIGS. 20-26, intervening material 57 has been formedlaterally-between and longitudinally-alongimmediately-laterally-adjacent memory blocks 58. Intervening material 57may provide lateral electrical isolation (insulation) betweenimmediately-laterally-adjacent memory-blocks. Such may include one ormore of insulative, semiconductive, and conducting materials and,regardless, may facilitate conductive tiers 22* from shorting relativeone another in a finished circuitry construction. Example insulativematerials are one or more of SiO₂, Si₃N₄, Al₂O₃, and undopedpolysilicon. Intervening material 57 may include through array vias(TAV's) and not shown. By way of example only, intervening material 57is shown as comprising a composite of insulating material 67 (e.g.,silicon nitride), insulating material 68 (e.g., silicon dioxide), andinsulative material 69 (e.g., undoped polysilicon). In one embodimentand as shown, intervening material 57 comprises insulating material(e.g., 67) that is directly against conductor material 17 of conductortier 16 and in one embodiment insulating material (e.g., 67) ofintervening material 57 projects laterally in direction 39 towardschannel-material strings 53 to be directly under now-lowest second tier20 x in what ultimately will be a finished circuitry construction.Further and regardless, in one embodiment and as shown, conductingmaterial 48 of first tiers 22* that are above lowest first tier 22 zprojects laterally in a direction 70 away from channel-material strings53 into insulating material (e.g., 67) of intervening material 57 in thefinished circuitry construction.

In one embodiment and as shown, lowest surface 71 (FIGS. 22 and 25) ofchannel material 36 of channel-material strings 53 is never directlyagainst any of conductor material 17 of conductor tier 16.

Conducting material 48 forms individual conductive lines 29 (e.g.,wordlines) and elevationally-extending strings 49 of individualtransistors and/or memory cells 56. Approximate locations of transistorsand/or memory cells 56 are indicated with a bracket in FIG. 26 and somewith dashed outlines in FIGS. 21, 23, 24, and 25, with transistorsand/or memory cells 56 being essentially ring-like or annular in thedepicted example. Alternately, transistors and/or memory cells 56 maynot be completely encircling relative to individual channel openings 25such that each channel opening 25 may have two or moreelevationally-extending strings 49 (e.g., multiple transistors and/ormemory cells about individual channel openings in individual conductivetiers with perhaps multiple wordlines per channel opening in individualconductive tiers, and not shown). Conducting material 48 may beconsidered as having terminal ends 50 (FIG. 26) corresponding tocontrol-gate regions 52 of individual transistors and/or memory cells56. Control-gate regions 52 in the depicted embodiment compriseindividual portions of individual conductive lines 29. Materials 30, 32,and 34 may be considered as a memory structure 65 that is laterallybetween control-gate region 52 and channel material 36. In oneembodiment and as shown with respect to the example “gate-last”processing, conducting material 48 of conductive tiers 22 is formedafter forming channel openings 25 and/or trenches 40. As alluded toabove, lowest first tier 22 z may be a select gate tier (e.g., nooperative memory cells being formed therein).

A charge-blocking region (e.g., charge-blocking material 30) is betweenstorage material 32 and individual control-gate regions 52. A chargeblock may have the following functions in a memory cell: In a programmode, the charge block may prevent charge carriers from passing out ofthe storage material (e.g., floating-gate material, charge-trappingmaterial, etc.) toward the control gate, and in an erase mode the chargeblock may prevent charge carriers from flowing into the storage materialfrom the control gate. Accordingly, a charge block may function to blockcharge migration between the control-gate region and the storagematerial of individual memory cells. An example charge-blocking regionas shown comprises insulator material 30. By way of further examples, acharge-blocking region may comprise a laterally (e.g., radially) outerportion of the storage material (e.g., material 32) where such storagematerial is insulative (e.g., in the absence of anydifferent-composition material between an insulative storage material 32and conducting material 48). Regardless, as an additional example, aninterface of a storage material and conductive material of a controlgate may be sufficient to function as a charge-blocking region in theabsence of any separate-composition-insulator material 30. Further, aninterface of conducting material 48 with material 30 (when present) incombination with insulator material 30 may together function as acharge-blocking region, and as alternately or additionally may alaterally-outer region of an insulative storage material (e.g., asilicon nitride material 32). An example material 30 is one or more ofsilicon hafnium oxide and silicon dioxide.

Any other attribute(s) or aspect(s) as shown and/or described hereinwith respect to other embodiments may be used in the embodiments shownand described with reference to the above embodiments.

Alternate embodiment constructions may result from method embodimentsdescribed above, or otherwise. Regardless, embodiments of the inventionencompass memory arrays independent of method of manufacture.Nevertheless, such memory arrays may have any of the attributes asdescribed herein in method embodiments. Likewise, the above-describedmethod embodiments may incorporate, form, and/or have any of theattributes described with respect to device embodiments.

In one embodiment, a memory array (e.g., 12) comprising strings (e.g.,49) of memory cells (e.g., 56) comprises a conductor tier (e.g., 16)comprising conductor material (e.g., 17). The memory array compriseslaterally-spaced memory blocks (e.g., 58) individually comprising avertical stack (e.g., 18) comprising alternating insulative tiers (e.g.,20*) and conductive tiers (e.g., 22*) directly above the conductor tier.Conducting material (e.g., 42) of a lowest conductive tier (e.g., 22 z)is directly against the conductor material of the conductor tier. In onesuch embodiment, the lowest of the conductive tiers is thicker than theconductive tiers there-above. Channel-material strings (e.g., 53) ofmemory cells (e.g., 56) extend through the insulative tier and theconductive tiers. Intervening material (e.g., 57) is laterally-betweenand longitudinally-along immediately-laterally-adjacent of the memoryblocks. The conducting material in the lowest conductive tier isdirectly against the channel material (e.g., 36) of individual of thechannel-material strings. The insulative tier (e.g., 20 x)immediately-above the lowest conductive tier comprises an upper firstinsulative material (e.g., 21) and a lower second insulative material(e.g., 23) under the upper first insulative material, with the lowersecond insulative material being of different composition from that ofthe upper first insulative material. In one such embodiment, the upperfirst insulative material comprises silicon dioxide and the lower secondinsulative material comprises undoped polysilicon. In one suchembodiment, the upper first insulative material comprises silicondioxide and the lower second insulative material comprises siliconnitride. In one such embodiment, the lower second insulative material isthinner than the upper first insulative material. In one suchembodiment, the lowest of the conductive tiers is thicker than theconductive tiers there-above. In one such embodiment, the interveningmaterial comprises insulating material that is directly against theconductor material of the conductor tier. In one such embodiment, theconductive material is directly against a sidewall (e.g., 41) of thechannel material of the individual channel-material strings. Any otherattribute(s) or aspect(s) as shown and/or described herein with respectto other embodiments may be used.

In one embodiment, a memory array (e.g., 12) comprising strings (e.g.,49) of memory cells (e.g., 56) comprises a conductor tier (e.g., 16)comprising conductor material (e.g., 17). The memory array compriseslaterally-spaced memory blocks (e.g., 58) individually comprising avertical stack (e.g., 18) comprising alternating insulative tiers (e.g.,20*) and conductive tiers (e.g., 22*) directly above the conductor tier.Conducting material (e.g., 42) of a lowest conductive tier (e.g., 22 z)is directly against the conductor material of the conductor tier. In onesuch embodiment, the lowest of the conductive tiers is thicker than theconductive tiers there-above. Channel-material strings (e.g., 53) ofmemory cells (e.g., 56) extend through the insulative tier and theconductive tiers. Intervening material (e.g., 57) is laterally-betweenand longitudinally-along immediately-laterally-adjacent of the memoryblocks. The conducting material in the lowest conductive tier isdirectly against the channel material (e.g., 36) of individual of thechannel-material strings. Conductive material (e.g., 23) of differentcomposition from that of the conducting material is above and directlyagainst the conducting material. In one such embodiment, the conductingmaterial comprises conductively-doped polysilicon and the conductivematerial comprises metal material. Any other attribute(s) or aspect(s)as shown and/or described herein with respect to other embodiments maybe used.

Where materials 23 and 42 are of the same composition in the finishedconstruction, such may not be discernible relative one another (e.g., aninterface there-between may not be discernible). Regardless, in oneembodiment, a memory array (e.g., 12) comprising strings (e.g., 49) ofmemory cells (e.g., 56) comprises a conductor tier (e.g., 16) comprisingconductor material (e.g., 17). The memory array compriseslaterally-spaced memory blocks (e.g., 58) individually comprising afirst vertical stack (e.g., 18) comprising alternating insulative tiers(e.g., 20*) and conductive tiers (e.g., 22*) directly above theconductor tier. Conducting material (e.g., 42) of a lowest conductivetier (e.g., 22 z) is directly against the conductor material of theconductor tier. Channel-material strings (e.g., 53) of memory cells(e.g., 56) extend through the insulative tier and the conductive tiers.Intervening material (e.g., 57) is laterally-between andlongitudinally-along immediately-laterally-adjacent of the memoryblocks. The conducting material in the lowest conductive tier isdirectly against the channel material (e.g., 36) of individual of thechannel-material strings. A second vertical stack is positionedlaterally of the first vertical stack. For example, consider FIG. 27 ascomprising part of the construction exemplified by FIGS. 20-26 andadditionally having a second vertical stack 75 positioned laterally offirst vertical stack 18. Such second vertical stack comprisesalternating first insulative tiers (e.g., 22*) and second insulativetiers (e.g., 20*), with a lowest of the first insulative tiers (e.g., 22z) being thicker than the first insulative tiers there-above. The firstinsulative tiers comprise first insulative material (e.g., 26) and thesecond insulative tiers comprising second insulative material (e.g., 21,24, and/or 27) of different composition from that of the firstinsulative tiers. The second insulative tier (e.g., 22 x) that isimmediately-above the lowest first insulative tier comprises an upperinsulative material (e.g., 21) and a lower material (e.g., 23) under theupper insulative material, with the lower material being of differentcomposition from that of the upper insulative material. In one suchembodiment, the second insulative tier that is immediately-above thelowest first insulative tier comprises a lowest insulative materialunder the lower material. For example, and by way of example only, sucha construction 10 of FIG. 27 (in combination with that of FIGS. 2 and20-26) may result in area where trenches 40 are not formed, wherebymaterial 26 is not there-removed. Any other attribute(s) or aspect(s) asshown and/or described herein with respect to other embodiments may beused.

The above processing(s) or construction(s) may be considered as beingrelative to an array of components formed as or within a single stack orsingle deck of such components above or as part of an underlying basesubstrate (albeit, the single stack/deck may have multiple tiers).Control and/or other peripheral circuitry for operating or accessingsuch components within an array may also be formed anywhere as part ofthe finished construction, and in some embodiments may be under thearray (e.g., CMOS under-array). Regardless, one or more additional suchstack(s)/deck(s) may be provided or fabricated above and/or below thatshown in the figures or described above. Further, the array(s) ofcomponents may be the same or different relative one another indifferent stacks/decks and different stacks/decks may be of the samethickness or of different thicknesses relative one another. Interveningstructure may be provided between immediately-vertically-adjacentstacks/decks (e.g., additional circuitry and/or dielectric layers).Also, different stacks/decks may be electrically coupled relative oneanother. The multiple stacks/decks may be fabricated separately andsequentially (e.g., one atop another), or two or more stacks/decks maybe fabricated at essentially the same time.

The assemblies and structures discussed above may be used in integratedcircuits/circuitry and may be incorporated into electronic systems. Suchelectronic systems may be used in, for example, memory modules, devicedrivers, power modules, communication modems, processor modules, andapplication-specific modules, and may include multilayer, multichipmodules. The electronic systems may be any of a broad range of systems,such as, for example, cameras, wireless devices, displays, chip sets,set top boxes, games, lighting, vehicles, clocks, televisions, cellphones, personal computers, automobiles, industrial control systems,aircraft, etc.

In this document unless otherwise indicated, “elevational”, “higher”,“upper”, “lower”, “top”, “atop”, “bottom”, “above”, “below”, “under”,“beneath”, “up”, and “down” are generally with reference to the verticaldirection. “Horizontal” refers to a general direction (i.e., within 10degrees) along a primary substrate surface and may be relative to whichthe substrate is processed during fabrication, and vertical is adirection generally orthogonal thereto. Reference to “exactlyhorizontal” is the direction along the primary substrate surface (i.e.,no degrees there-from) and may be relative to which the substrate isprocessed during fabrication. Further, “vertical” and “horizontal” asused herein are generally perpendicular directions relative one anotherand independent of orientation of the substrate in three-dimensionalspace. Additionally, “elevationally-extending” and “extend(ing)elevationally” refer to a direction that is angled away by at least 45°from exactly horizontal. Further, “extend(ing) elevationally”,“elevationally-extending”, “extend(ing) horizontally”,“horizontally-extending” and the like with respect to a field effecttransistor are with reference to orientation of the transistor's channellength along which current flows in operation between the source/drainregions. For bipolar junction transistors, “extend(ing) elevationally”“elevationally-extending”, “extend(ing) horizontally”,“horizontally-extending” and the like, are with reference to orientationof the base length along which current flows in operation between theemitter and collector. In some embodiments, any component, feature,and/or region that extends elevationally extends vertically or within10° of vertical.

Further, “directly above”, “directly below”, and “directly under”require at least some lateral overlap (i.e., horizontally) of two statedregions/materials/components relative one another. Also, use of “above”not preceded by “directly” only requires that some portion of the statedregion/material/component that is above the other be elevationallyoutward of the other (i.e., independent of whether there is any lateraloverlap of the two stated regions/materials/components). Analogously,use of “below” and “under” not preceded by “directly” only requires thatsome portion of the stated region/material/component that is below/underthe other be elevationally inward of the other (i.e., independent ofwhether there is any lateral overlap of the two statedregions/materials/components).

Any of the materials, regions, and structures described herein may behomogenous or non-homogenous, and regardless may be continuous ordiscontinuous over any material which such overlie. Where one or moreexample composition(s) is/are provided for any material, that materialmay comprise, consist essentially of, or consist of such one or morecomposition(s). Further, unless otherwise stated, each material may beformed using any suitable existing or future-developed technique, withatomic layer deposition, chemical vapor deposition, physical vapordeposition, epitaxial growth, diffusion doping, and ion implanting beingexamples.

Additionally, “thickness” by itself (no preceding directional adjective)is defined as the mean straight-line distance through a given materialor region perpendicularly from a closest surface of animmediately-adjacent material of different composition or of animmediately-adjacent region. Additionally, the various materials orregions described herein may be of substantially constant thickness orof variable thicknesses. If of variable thickness, thickness refers toaverage thickness unless otherwise indicated, and such material orregion will have some minimum thickness and some maximum thickness dueto the thickness being variable. As used herein, “different composition”only requires those portions of two stated materials or regions that maybe directly against one another to be chemically and/or physicallydifferent, for example if such materials or regions are not homogenous.If the two stated materials or regions are not directly against oneanother, “different composition” only requires that those portions ofthe two stated materials or regions that are closest to one another bechemically and/or physically different if such materials or regions arenot homogenous. In this document, a material, region, or structure is“directly against” another when there is at least some physical touchingcontact of the stated materials, regions, or structures relative oneanother. In contrast, “over”, “on”, “adjacent”, “along”, and “against”not preceded by “directly” encompass “directly against” as well asconstruction where intervening material(s), region(s), or structure(s)result(s) in no physical touching contact of the stated materials,regions, or structures relative one another.

Herein, regions-materials-components are “electrically coupled” relativeone another if in normal operation electric current is capable ofcontinuously flowing from one to the other and does so predominately bymovement of subatomic positive and/or negative charges when such aresufficiently generated. Another electronic component may be between andelectrically coupled to the regions-materials-components. In contrast,when regions-materials-components are referred to as being “directlyelectrically coupled”, no intervening electronic component (e.g., nodiode, transistor, resistor, transducer, switch, fuse, etc.) is betweenthe directly electrically coupled regions-materials-components.

Any use of “row” and “column” in this document is for convenience indistinguishing one series or orientation of features from another seriesor orientation of features and along which components have been or maybe formed. “Row” and “column” are used synonymously with respect to anyseries of regions, components, and/or features independent of function.Regardless, the rows may be straight and/or curved and/or parallelacid/or not parallel relative one another, as may be the columns.Further, the rows and columns may intersect relative one another at 90°or at one or more other angles (i.e., other than the straight angle).

The composition of any of the conductive/conductor/conducting materialsherein may be metal material and/or conductively-dopedsemiconductive/semiconductor/semiconducting material. “Metal material”is any one or combination of an elemental metal, any mixture or alloy oftwo or more elemental metals, and any one or more conductive metalcompound(s).

Herein, any use of “selective” as to etch, etching, removing, removal,depositing, forming, and/or formation is such an act of one statedmaterial relative to another stated material(s) so acted upon at a rateof at least 2:1 by volume. Further, any use of selectively depositing,selectively growing, or selectively forming is depositing, growing, orforming one material relative to another stated material or materials ata rate of at least 2:1 by volume for at least the first 75 Angstroms ofdepositing, growing, or forming.

Unless otherwise indicated, use of “or” herein encompasses either andboth.

CONCLUSION

In some embodiments, a method used in forming a memory array comprisingstrings of memory cells comprises forming a conductor tier comprisingconductor material on a substrate. A stack comprisingvertically-alternating first tiers and second tiers is formed above theconductor tier. The stack comprises laterally-spaced memory-blockregions having horizontally-elongated trenches there-between.Channel-material strings extend through the first tiers and the secondtiers. Material of the first tiers is of different composition from thatof the second tiers. A lowest of the first tiers is thicker than thefirst tiers there-above. The second-tier material of the second tierthat is immediately-above the lowest first tier comprises an upper firstinsulative material and a lower second material under the upper firstinsulative material. The lower second material is of differentcomposition from that of the upper first insulative material. Thefirst-tier material is isotropically etched selectively relative to thesecond-tier material to form void-space in the first tiers. Conductingmaterial is deposited into the trenches and into the void-space in thefirst tiers. The conducting material fills the void-space in the firsttiers that are above the lowest first tier. The conducting materialless-than-fills the void-space in the lowest first tier. The conductingmaterial is etched from the lowest first tier. After the conductingmaterial is etched, conductive material is deposited into the void-spaceof the lowest first tier under the lower second material in the secondtier that is immediately-above the lowest first tier. The conductivematerial directly electrically couples together the channel material ofindividual of the channel-material strings and the conductor material ofthe conductor tier.

In some embodiments, a method used in forming a memory array comprisingstrings of memory cells comprises forming a conductor tier comprisingconductor material on a substrate. A stack comprisingvertically-alternating first tiers and second tiers is formed above theconductor tier. The stack comprises laterally-spaced memory-blockregions having horizontally-elongated trenches there-between.Channel-material strings extend through the first tiers and the secondtiers. Material of the first tiers is of different composition from thatof the second tiers. A lowest of the first tiers is thicker than thefirst tiers there-above. The second-tier material of the second tierthat is immediately-above the lowest first tier comprises an upperinsulative material, a lower material, and an intermediate materialvertically-between the upper insulative material and the lower material.The intermediate material is of different composition from that of thelower material and from that of the upper insulative material. Thefirst-tier material is isotropically etched selectively relative to thesecond-tier material to form void-space in the first tiers. Conductingmaterial is deposited into the trenches and into the void-space in thefirst tiers. The conducting material fills the void-space in the firsttiers that are above the lowest first tier. The conducting materialless-than-fills the void-space in the lowest first tier. The conductingmaterial is etched from the lowest first tier selectively relative tothe lower material in the second tier that is immediately-above thelowest first tier to leave the lower material under the intermediatematerial in the second tier that is immediately-above the lowest firsttier. After the conducting material is etched, the lower material in thesecond tier that is immediately-above the lowest first tier is etchedselectively relative to and to expose a lower surface of theintermediate material. After the etching of the lower material in thesecond tier that is immediately-above the lowest first tier, conductivematerial is deposited into the void-space of the lowest first tier underthe intermediate material in the second tier that is immediately-abovethe lowest first tier. The conductive material directly electricallycouples together the channel material of individual of thechannel-material strings and the conductor material of the conductortier.

In some embodiments, a memory array comprising strings of memory cellscomprises a conductor tier comprising conductor material. The memoryarray comprises laterally-spaced memory blocks individually comprising avertical stack comprising alternating insulative tiers and conductivetiers directly above the conductor tier. Conducting material of a lowestof the conductive tiers is directly against the conductor material ofthe conductor tier. Channel-material strings of memory cells extendthrough the insulative tiers and the conductive tiers. Interveningmaterial is laterally-between and longitudinally-alongimmediately-laterally-adjacent of the memory blocks. The conductingmaterial in the lowest conductive tier is directly against the channelmaterial of individual of the channel-material strings. The insulativetier immediately-above the lowest conductive tier comprises an upperfirst insulative material and a lower second insulative material underthe upper first insulative material. The lower second insulativematerial is of different composition from that of the upper firstinsulative material.

In some embodiments, a memory array comprising strings of memory cellscomprises a conductor tier comprising conductor material. The memoryarray comprises laterally-spaced memory blocks individually comprising avertical stack comprising alternating insulative tiers and conductivetiers directly above the conductor tier. Conducting material of a lowestof the conductive tiers is directly against the conductor material ofthe conductor tier. Channel-material strings of memory cells extendthrough the insulative tiers and the conductive tiers. Interveningmaterial is laterally-between and longitudinally-alongimmediately-laterally-adjacent of the memory blocks. The conductingmaterial in the lowest conductive tier is directly against the channelmaterial of individual of the channel-material strings. Conductivematerial is of different composition from that of the conductingmaterial above and directly against the conducting material.

In some embodiments, a memory array comprising strings of memory cellscomprises a conductor tier comprising conductor material. The memoryarray comprises laterally-spaced memory blocks individually comprising afirst vertical stack comprising alternating insulative tiers andconductive tiers directly above the conductor tier. Conducting materialof a lowest of the conductive tiers is directly against the conductormaterial of the conductor tier. Channel-material strings of memory cellsextend through the insulative tiers and the conductive tiers.Intervening material is laterally-between and longitudinally-alongimmediately-laterally-adjacent of the memory blocks. The conductingmaterial in the lowest conductive tier is directly against the channelmaterial of individual of the channel-material strings. A secondvertical stack is laterally of the first vertical stack. The secondvertical comprises alternating first insulative tiers and secondinsulative tiers. A lowest of the first insulative tiers is thicker thanthe first insulative tiers there-above. The first insulative tierscomprise first insulative material. The second insulative tiers comprisesecond insulative material of different composition from that of thefirst insulative tiers. The second insulative tier that isimmediately-above the lowest first insulative tier comprises an upperinsulative material and a lower material under the upper insulativematerial. The lower material is of different composition from that ofthe upper insulative material.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

1. A method used in forming a memory array comprising strings of memorycells, comprising: forming a conductor tier comprising conductormaterial on a substrate; forming a stack comprisingvertically-alternating first tiers and second tiers above the conductortier, the stack comprising laterally-spaced memory-block regions havinghorizontally-elongated trenches there-between, channel-material stringsextending through the first tiers and the second tiers, material of thefirst tiers being of different composition from that of the secondtiers, a lowest of the first tiers being thicker than the first tiersthere-above, the second-tier material of the second tier that isimmediately-above the lowest first tier comprising an upper firstinsulative material and a lower second material under the upper firstinsulative material, the lower second material being of differentcomposition from that of the upper first insulative material;isotropically etching the first-tier material selectively relative tothe second-tier material to form void-space in the first tiers;depositing conducting material into the trenches and into the void-spacein the first tiers, the conducting material filling the void-space inthe first tiers that are above the lowest first tier, the conductingmaterial less-than-filling the void-space in the lowest first tier;etching the conducting material from the lowest first tier; and afterthe etching of the conducting material, depositing conductive materialinto the void-space of the lowest first tier under the lower secondmaterial in the second tier that is immediately-above the lowest firsttier, the conductive material directly electrically coupling togetherthe channel material of individual of the channel-material strings andthe conductor material of the conductor tier.
 2. The method of claim 1comprising etching away all of the conducting material that is in thetrenches before depositing the conductive material.
 3. The method ofclaim 1 wherein at least an uppermost portion of the conductor materialof the conductor tier is of the same composition as the conductivematerial.
 4. The method of claim 1 wherein the lowest first tier is atleast 1.5 times thicker than the first tiers there-above.
 5. The methodof claim 1 wherein the lowest first tier is not directly against theconductor material of the conductor tier during the isotropicallyetching.
 6. The method of claim 5 wherein a lowest of the second tiersis vertically between the conductor material of the conductor tier andthe lowest first tier during the isotropically etching.
 7. The method ofclaim 6 wherein the lowest second tier is thinner than the second tiersthere-above during the isotropically etching.
 8. The method of claim 7wherein the second tier that is immediately-above the lowest first tieris thicker than the second tiers there-above during the isotropicallyetching.
 9. The method of claim 1 wherein the conductive material is ofdifferent composition from that of at least an uppermost portion of theconductor material of the conductor tier.
 10. The method of claim 1wherein a lowest surface of the channel material of the channel-materialstrings is never directly against any of the conductor material of theconductor tier.
 11. The method of claim 1 wherein the conductivematerial in the void-space of the lowest first tier is directly againsta sidewall of the channel material of the channel-material strings. 12.The method of claim 1 wherein the conductive material in the void-spaceof the lowest first tier is directly against an uppermost surface of theconductor material of the conductor tier.
 13. The method of claim 1wherein the lower second material comprises at least one ofconductively-doped polysilicon, polysilicon that is not conductivelydoped, carbon-doped polysilicon, silicon nitride, undoped siliconnitride, carbon-doped silicon nitride, and metal material.
 14. Themethod of claim 1 wherein the lower second material is thinner than theupper first insulative material.
 15. The method of claim 1 wherein theconductive material is directly against the lower second material in thesecond tier that is immediately-above the lowest first tier.
 16. Amethod used in forming a memory array comprising strings of memorycells, comprising: forming a conductor tier comprising conductormaterial on a substrate; forming a stack comprisingvertically-alternating first tiers and second tiers above the conductortier, the stack comprising laterally-spaced memory-block regions havinghorizontally-elongated trenches there-between, channel-material stringsextending through the first tiers and the second tiers, material of thefirst tiers being of different composition from that of the secondtiers, a lowest of the first tiers being thicker than the first tiersthere-above; the second-tier material of the second tier that isimmediately-above the lowest first tier comprising an upper insulativematerial, a lower material, and an intermediate materialvertically-between the upper insulative material and the lower material;the intermediate material being of different composition from that ofthe lower material and from that of the upper insulative material;isotropically etching the first-tier material selectively relative tothe second-tier material to form void-space in the first tiers;depositing conducting material into the trenches and into the void-spacein the first tiers, the conducting material filling the void-space inthe first tiers that are above the lowest first tier, the conductingmaterial less-than-filling the void-space in the lowest first tier;etching the conducting material from the lowest first tier selectivelyrelative to the lower material in the second tier that isimmediately-above the lowest first tier to leave the lower materialunder the intermediate material in the second tier that isimmediately-above the lowest first tier; after the etching of theconducting material, etching the lower material in the second tier thatis immediately-above the lowest first tier selectively relative to andto expose a lower surface of the intermediate material; and after theetching of the lower material in the second tier that isimmediately-above the lowest first tier, depositing conductive materialinto the void-space of the lowest first tier under the intermediatematerial in the second tier that is immediately-above the lowest firsttier, the conductive material directly electrically coupling togetherthe channel material of individual of the channel-material strings andthe conductor material of the conductor tier.
 17. The method of claim 16wherein the intermediate material comprises at least one ofconductively-doped polysilicon, polysilicon that is not conductivelydoped, carbon-doped polysilicon, silicon nitride, undoped siliconnitride, carbon-doped silicon nitride, and metal material.
 18. Themethod of claim 16 wherein the intermediate material is thinner than theupper insulative material and the lower material.
 19. The method ofclaim 16 wherein the conductive material is directly against theintermediate material in the second tier that is immediately-above thelowest first tier.
 20. A memory array comprising strings of memorycells, comprising: a conductor tier comprising conductor material;laterally-spaced memory blocks individually comprising a vertical stackcomprising alternating insulative tiers and conductive tiers directlyabove the conductor tier, conducting material of a lowest of theconductive tiers being directly against the conductor material of theconductor tier, channel-material strings of memory cells extendingthrough the insulative tiers and the conductive tiers; interveningmaterial laterally-between and longitudinally-alongimmediately-laterally-adjacent of the memory blocks; the conductingmaterial in the lowest conductive tier being directly against thechannel material of individual of the channel-material strings; and theinsulative tier immediately-above the lowest conductive tier comprisingan upper first insulative material and a lower second insulativematerial under the upper first insulative material, the lower secondinsulative material being of different composition from that of theupper first insulative material. 21-26. (canceled)
 27. A memory arraycomprising strings of memory cells, comprising: a conductor tiercomprising conductor material; laterally-spaced memory blocksindividually comprising a vertical stack comprising alternatinginsulative tiers and conductive tiers directly above the conductor tier,conducting material of a lowest of the conductive tiers being directlyagainst the conductor material of the conductor tier, channel-materialstrings of memory cells extending through the insulative tiers and theconductive tiers; intervening material laterally-between andlongitudinally-along immediately-laterally-adjacent of the memoryblocks; and the conducting material in the lowest conductive tier beingdirectly against the channel material of individual of thechannel-material strings, conductive material of different compositionfrom that of the conducting material above and directly against theconducting material. 28-31. (canceled)
 32. A memory array comprisingstrings of memory cells, comprising: a conductor tier comprisingconductor material; laterally-spaced memory blocks individuallycomprising a first vertical stack comprising alternating insulativetiers and conductive tiers directly above the conductor tier, conductingmaterial of a lowest of the conductive tiers being directly against theconductor material of the conductor tier, channel-material strings ofmemory cells extending through the insulative tiers and the conductivetiers; intervening material laterally-between and longitudinally-alongimmediately-laterally-adjacent of the memory blocks; the conductingmaterial in the lowest conductive tier being directly against thechannel material of individual of the channel-material strings; and asecond vertical stack laterally of the first vertical stack, the secondvertical comprising: alternating first insulative tiers and secondinsulative tiers, a lowest of the first insulative tiers being thickerthan the first insulative tiers there-above, the first insulative tierscomprising first insulative material, the second insulative tierscomprising second insulative material of different composition from thatof the first insulative tiers; and the second insulative tier that isimmediately-above the lowest first insulative tier comprising an upperinsulative material and a lower material under the upper insulativematerial, the lower material being of different composition from that ofthe upper insulative material. 33-44. (canceled)